1. Field of the Invention
The present invention relates to a control device for a DC brushless motor or the like, and, in particular, to an over-heat protection of the motor.
2. Description of the Related Art
Conventionally, there has been an over-heat protecting device for an AC servo motor disclosed in, for example, Japanese Patent Unexamined Publication No. Sho 62-239822. In this conventional device, when it is judged that a motor is servo-locked, the electrification of the motor is interrupted so that the motor is protected from being over-heated in accordance with a predetermined characteristic corresponding to a stop position.
The above-described conventional device is applicable to a case where there arises no problem even if the electrification of the motor is interrupted at the time of over-heating. However, if the above-described conventional device is applied to a motor control device that does not allow a rapid change in torque, such as an electric power steering device, there arises a problem in that a steering feeling is rapidly changed at the time of performing the over-heat protection.